/*
 * Copyright (C) 2014 Rob Clark <robclark@freedesktop.org>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 * Authors:
 *    Rob Clark <robclark@freedesktop.org>
 */

#include "util/u_math.h"

#include "ir3.h"
#include "ir3_shader.h"

/*
 * Dead code elimination:
 */

static void
mark_array_use(struct ir3_instruction *instr, struct ir3_register *reg)
{
	if (reg->flags & IR3_REG_ARRAY) {
		struct ir3_array *arr =
			ir3_lookup_array(instr->block->shader, reg->array.id);
		arr->unused = false;
	}
}

static void
instr_dce(struct ir3_instruction *instr, bool falsedep)
{
	/* don't mark falsedep's as used, but otherwise process them normally: */
	if (!falsedep)
		instr->flags &= ~IR3_INSTR_UNUSED;

	if (ir3_instr_check_mark(instr))
		return;

	if (writes_gpr(instr))
		mark_array_use(instr, instr->regs[0]);   /* dst */

	foreach_src (reg, instr)
		mark_array_use(instr, reg);              /* src */

	foreach_ssa_src_n (src, i, instr) {
		instr_dce(src, __is_false_dep(instr, i));
	}
}

static bool
remove_unused_by_block(struct ir3_block *block)
{
	bool progress = false;
	foreach_instr_safe (instr, &block->instr_list) {
		if (instr->opc == OPC_END || instr->opc == OPC_CHSH || instr->opc == OPC_CHMASK)
			continue;
		if (instr->flags & IR3_INSTR_UNUSED) {
			if (instr->opc == OPC_META_SPLIT) {
				struct ir3_instruction *src = ssa(instr->regs[1]);
				/* tex (cat5) instructions have a writemask, so we can
				 * mask off unused components.  Other instructions do not.
				 */
				if (src && is_tex_or_prefetch(src) && (src->regs[0]->wrmask > 1)) {
					src->regs[0]->wrmask &= ~(1 << instr->split.off);

					/* prune no-longer needed right-neighbors.  We could
					 * probably do the same for left-neighbors (ie. tex
					 * fetch that only need .yw components), but that
					 * makes RA a bit more confusing than it already is
					 */
					struct ir3_instruction *n = instr;
					while (n && n->cp.right)
						n = n->cp.right;
					while (n->flags & IR3_INSTR_UNUSED) {
						n = n->cp.left;
						if (!n)
							break;
						n->cp.right = NULL;
					}
				}
			}

			/* prune false-deps, etc: */
			foreach_ssa_use (use, instr)
				foreach_ssa_srcp_n (srcp, n, use)
					if (*srcp == instr)
						*srcp = NULL;

			list_delinit(&instr->node);
			progress = true;
		}
	}
	return progress;
}

static bool
find_and_remove_unused(struct ir3 *ir, struct ir3_shader_variant *so)
{
	unsigned i;
	bool progress = false;

	ir3_clear_mark(ir);

	/* initially mark everything as unused, we'll clear the flag as we
	 * visit the instructions:
	 */
	foreach_block (block, &ir->block_list) {
		foreach_instr (instr, &block->instr_list) {
			/* special case, if pre-fs texture fetch used, we cannot
			 * eliminate the barycentric i/j input
			 */
			if (so->num_sampler_prefetch &&
					(instr->opc == OPC_META_INPUT) &&
					(instr->input.sysval == SYSTEM_VALUE_BARYCENTRIC_PERSP_PIXEL))
				continue;
			instr->flags |= IR3_INSTR_UNUSED;
		}
	}

	foreach_array (arr, &ir->array_list)
		arr->unused = true;

	foreach_block (block, &ir->block_list) {
		for (i = 0; i < block->keeps_count; i++)
			instr_dce(block->keeps[i], false);

		/* We also need to account for if-condition: */
		if (block->condition)
			instr_dce(block->condition, false);
	}

	/* remove un-used instructions: */
	foreach_block (block, &ir->block_list) {
		progress |= remove_unused_by_block(block);
	}

	/* remove un-used arrays: */
	foreach_array_safe (arr, &ir->array_list) {
		if (arr->unused)
			list_delinit(&arr->node);
	}

	/* fixup wrmask of split instructions to account for adjusted tex
	 * wrmask's:
	 */
	foreach_block (block, &ir->block_list) {
		foreach_instr (instr, &block->instr_list) {
			if (instr->opc != OPC_META_SPLIT)
				continue;

			struct ir3_instruction *src = ssa(instr->regs[1]);
			if (!is_tex_or_prefetch(src))
				continue;

			instr->regs[1]->wrmask = src->regs[0]->wrmask;
		}
	}

	/* note that we can end up with unused indirects, but we should
	 * not end up with unused predicates.
	 */
	for (i = 0; i < ir->a0_users_count; i++) {
		struct ir3_instruction *instr = ir->a0_users[i];
		if (instr && (instr->flags & IR3_INSTR_UNUSED))
			ir->a0_users[i] = NULL;
	}

	for (i = 0; i < ir->a1_users_count; i++) {
		struct ir3_instruction *instr = ir->a1_users[i];
		if (instr && (instr->flags & IR3_INSTR_UNUSED))
			ir->a1_users[i] = NULL;
	}

	/* cleanup unused inputs: */
	foreach_input_n (in, n, ir)
		if (in->flags & IR3_INSTR_UNUSED)
			ir->inputs[n] = NULL;

	return progress;
}

bool
ir3_dce(struct ir3 *ir, struct ir3_shader_variant *so)
{
	void *mem_ctx = ralloc_context(NULL);
	bool progress, made_progress = false;

	ir3_find_ssa_uses(ir, mem_ctx, true);

	do {
		progress = find_and_remove_unused(ir, so);
		made_progress |= progress;
	} while (progress);

	ralloc_free(mem_ctx);

	return made_progress;
}
